Power splitters/combiners are essential components in optical systems, and especially in integrated planar waveguide systems. U.S. patent application Ser. No. 10/093,663 describes a splitter/combiner system with improved tolerance to parameter deviations. In this power splitter/combiner system, each splitter/combiner is comprised of two or more directional couplers serially connected to two or more phase shifts in an alternating order (e.g., directional coupler, phase shift, directional coupler, phase shift, directional coupler). The specific coupling and phase values for the directional couplers and phase shifts are selected to minimize changes in an output signal in response to changes in the coupling coefficients and the propagation constants, for example.
In one embodiment, a parameter tolerant 50/50 splitter/combiner is provided for an external system having frequency dependent transmission and reflection properties.